The present invention relates to non-invasive probes for application to a body part of a subject for the detection of a medical condition of the subject. The invention is particularly useful in finger probes, such as described in U.S. Pat. Nos. 6,319,205 and 6,322,515, and in International Applications PCT/IL99/00292 (published Dec. 16, 1999 as International Publication No. WO 99/63884), PCT/IL00/00307 published Dec. 14, 2000 as International Publication No. WO 00/74551), PCT/IL00/00403 (published Jan. 18, 2001 as International Publication No. WO 01/03569; and PCT/IL01/00970, filed Oct. 22, 2001. The invention is therefore described below with respect to the probes described in the above patents and applications (hereinafter, “the above-identified U.S. patents and International Patent Applications”), but it will be appreciated that the invention could also be advantageously used in other types of probes.
The above-identified U.S. patents and International Patent Applications disclose various probe constructions, methods and apparatus for the non-invasive detection of a medical condition of a subject, particularly by monitoring changes in the peripheral arterial tone as manifested by changes in the pulsatile arterial blood volume in a terminal extremity of a body part, e.g., a digit (finger or toe) of the subject. The various medical conditions detected by such probes, as described therein, include mycardial ischemia, sleep apnea, endothelial dysfunction (ED), sleep disorders, mental stress, sympathetic nervous system reactivity, blood pressure, etc.
In general, the probes described in the above-identified U.S. patents and International Applications include a housing defining a compartment closed at one end and open at the opposite end for receiving the distal end of the subject's body part, such as a finger or toe, including its terminal-most extremity, and a sensor for sensing a predetermined condition of the body part after being received within the compartment. The preferred embodiments described therein are particularly useful for monitoring peripheral arterial tone in a subject's finger, and for this purpose, they include pressurizing means for applying a static pressure field substantially uniformly around the distal end of the subject's finger, including its terminal-most extremity. The pressure field is of a predetermined magnitude sufficient to substantially prevent distention of the venous vasculature, uncontrolled venous backflow and retrogade shockwave propagation into the distal end of the finger, and to partially unload the wall tension of, but not to occlude, the arteries in the distal end of the finger when at heart level or below. The probe sensor senses changes in the distal end of the subject's finger (or other body part) related to changes in volume therein due to pulsatile changes in instantaneous blood volume related to arterial tone.
Further particulars as to the construction of such probes, and the various medical conditions for which they may be used, are available in the above-identified U.S. patents and International Patent Applications, the contents of which are hereby incorporated by reference herein.
Because of the potential diagnostic capabilities of such probes, considerable research and development has been conducted to improve their construction, to make them more convenient to use, and to extend their diagnostic range.